Numerical and experimental investigation of a two-dimensional laminar flow with non-regular boundaries
Numerical analysis of two-dimensional laminar flow with nonregular boundaries
NAVIER-STOKES EQUATION↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Determination of gas bearing stability by response to a step-jump Interim report
Numerical analysis of gas bearing stability based on bearing film step-jump responses, and use of Duhamel theorem
STEP FUNCTION↗
Correlations between emission events in Rainbow Gravity
Highlights: • It is studied emission correlations between particle emission events in black holes. • Particles emitted have highly correlated moments before the BH stops radiating. • Rainbow Gravity allows maintaining the rest of it stored in its remnant. In this work, we study emission correlations in Rainbow Gravity (RG) black holes known to have black hole remnants. Non-thermal corrections are responsible for generating non-zero correlations between particle emission events during the black hole evaporation process. With this in mind, we calculate the temperatures considering back-reaction effects. Then, we obtain the correlations between emission events for a RG metric proposed by Magueijo and Smolin. We also discuss through a numerical analysis the emission correlations behavior in the last stages of evaporation of the black hole.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Finite element analysis of moisture effects in graphite-epoxy composites
A numerical analysis procedure is developed for the micro-mechanical investigation of moisture effects on graphite-epoxy composites. The procedure employs a nonlinear constitutive relationship in a finite element formulation. A quasi-Newton method is used to solve the resulting nonlinear algebraic equations. The results presented indicate that the stresses at the graphite-epoxy interface have a strong dependence on moisture content, fiber spacing, and applied load.
Tobing, F. E. L.↗
ICASE semiannual report, April 1 - September 30, 1989
The Institute conducts unclassified basic research in applied mathematics, numerical analysis, and computer science in order to extend and improve problem-solving capabilities in science and engineering, particularly in aeronautics and space. The major categories of the current Institute for Computer Applications in Science and Engineering (ICASE) research program are: (1) numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; (2) control and parameter identification problems, with emphasis on effective numerical methods; (3) computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and (4) computer systems and software, especially vector and parallel computers. ICASE reports are considered to be primarily preprints of manuscripts that have been submitted to appropriate research journals or that are to appear in conference proceedings.
Source record↗
Quasinormal modes and shadow of a Schwarzschild black hole with GUP
Highlights: • The physics of quantum corrected Schwarzschild Black Hole via GUP is investigated. • Quasinormal Modes (QNM) are obtained via WKB and numeric methods. • The relationship between shadow and QNM in the eikonal limit is established. • The quadratic and linear GUP parameters affect the results in a clear way. We consider quantum corrections for the Schwarzschild black hole metric by using the generalized uncertainty principle (GUP) to investigate quasinormal modes, shadow and their relationship in the eikonal limit. We calculate the quasinormal frequencies of the quantum-corrected Schwarzschild black hole by using the sixth-order Wentzel–Kramers–Brillouin (WKB) approximation, and also perform a numerical analysis that confirms the results obtained from this approach. We also find that the shadow radius is nonzero even at very small mass limit for finite GUP parameter.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
RandONets: Shallow networks with random projections for learning linear and nonlinear operators
Deep neural networks have been extensively used for the solution of both the forward and the inverse problem for dynamical systems. However, their implementation necessitates optimizing a high-dimensional space of parameters and hyperparameters. This fact, along with the requirement of substantial computational resources, pose a barrier to achieving high numerical accuracy, but also interpretability. Here, to address the above challenges, we present Random Projection-based Operator Networks (RandONets): shallow networks with random projections and tailor-made numerical analysis methods that learn accurately and fast linear and nonlinear operators. Building on previous works, we prove that RandOnets are universal approximators of linear and nonlinear operators. Due to their simplicity, RandONets provide a one-step transformation of the input space, facilitating interpretability. For the evaluation of their performance, we focus on operators of PDEs. We show, that RandONets outperform by several orders of magnitude, both in terms of numerical approximation accuracy and computational cost, the “vanilla” DeepONets. Hence, we believe that our method will trigger further developments in the field of scientific machine learning, for the development of new ‘’light”schemes that will provide high accuracy while reducing dramatically the computational cost. A MATLAB toolbox for RandONets, including demos, is available on GitHub at https://github.com/GianlucaFabiani/RandONets.
Interpretable machine learning↗
The effect of unsteadiness on the time-mean thermal loads in a turbine stage
Two steady numerical analysis methods and one unsteady method are used to study the viscous three-dimensional flow in the middle stage of the Pratt & Whitney alternate design Space Shuttle Main Engine fuel turbine. The principal characteristic of this flow is that the secondary flows generated in the rotor blade reconfigure a radial inlet total temperature distortion into one with a pitchwise exit hot streak distortion. Secondary flows in the following vane redistribute the radial variation while unsteadiness causes a segregation of hot and cold flow from the hot streak within the vane. Such redistribution and segregation can lead to unexpected thermal loads and reduced durability. The physical phenomena and the ability of a steady analysis to capture them are investigated by performing a numerical experiment whereby the results of the two steady analysis methods are compared to the time-mean of the unsteady simulation. The flow physics related to the segregation and mixing of total temperature are discussed.
Kirtley, K. R.↗
Global function approach in structural analysis: Basic approach, numerical results
The structural response to a given environment is described by the differential equations of motion of deformable bodies. Analytic solutions of such problems for a reasonably large class of structural configurations are not within the realm of the possible. Consequently, the mathematical problem is recast into a numerical problem for solution on the computer. New technology in the space and energy fields led to a growing demand for accurate analysis which at times cannot be met due to the limits set by available budgets for computer time. In response to this need for more efficient numerical analysis, the possibilities of reducing the number of freedoms in the system through a revival of the global function approach were explored.
Almroth, B. O.↗
Virtual prototyping of liquid metal blanket performance in fusion pilot plant
Liquid metal blanket is a dominant design option for the next step fusion devices responsible for harvesting energy from fusion reaction, and simultaneously producing fuel for the same reaction through tritium breeding. Liquid metal blankets introduce additional complexity to the design due to fluid motion, fluid structure interaction, and magnetohydrodynamic (MHD) effects arising from the motion of the conducting fluid through the magnetic field. They are also directly affected by the plasma heat flux and neutronic fluence. PPPL is currently developing a virtual prototyping system for numerical analysis of the liquid metal blankets for future fusion devices. The system has a customized 3D computational fluid dynamics (CFD) code in its core, allowing MHD flow and conjugate heat transfer analysis in blankets fluids and solids. The code was successfully used before for dual coolant blanket analysis [A. Khodak et al., Fusion Eng. and Des. 137 (2018)]. Recently the same code was modified to allow verified simulation of MHD flows at high Hartmann numbers of several thousand typical for blanket applications. CFD code receives volumetric heat source distribution from the neutronic analysis based on MCNP code. In addition, direct tritium breeding simulation will be performed allowing optimization of the blanket performance. 2D axisymmetric version of neutronics code will be used for rapid optimization, with 3D version employed for detailed analysis. The surface heat distribution on the plasma facing wall will be defined by the software HEAT allowing 3D modeling of the heat flux based on the magnetic field distribution including gyro-orbit effects. Results of thermal analysis are imported into structural analysis code also included in the system. Finally, direct import of CAD geometry will be used for analyzing all components and as a result design option can be efficiently optimized.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Simulation of femtosecond interferometry when studying the effect of intense laser irradiation of a transparent medium
A method for comparing experimental and simulation results obtained when transmitting a femtosecond laser pulse through a material is proposed. This method is based on computer reproduction of photographs recorded using femtosecond interferometry. A numerical analysis of the spatial and temporal evolution of an intense (∼10{sup 13} W cm{sup −2}) pulse propagating in the bulk of yttrium aluminium garnet is presented. (paper)
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Task 7: Endwall treatment inlet flow distortion analysis
The overall objective of this study was to develop a 3-D numerical analysis for compressor casing treatment flowfields, and to perform a series of detailed numerical predictions to assess the effectiveness of various endwall treatments for enhancing the efficiency and stall margin of modern high speed fan rotors. Particular attention was given to examining the effectiveness of endwall treatments to counter the undesirable effects of inflow distortion. Calculations were performed using three different gridding techniques based on the type of casing treatment being tested and the level of complexity desired in the analysis. In each case, the casing treatment itself is modeled as a discrete object in the overall analysis, and the flow through the casing treatment is determined as part of the solution. A series of calculations were performed for both treated and untreated modern fan rotors both with and without inflow distortion. The effectiveness of the various treatments were quantified, and several physical mechanisms by which the effectiveness of endwall treatments is achieved are discussed.
Hall, E. J.↗
A numerical model for dynamic wave rotor analysis
A numerical model has been developed which can predict the dynamic (and steady state) performance of a wave rotor, given the geometry and time dependent boundary conditions. The one-dimensional, perfect gas, CFD based code tracks the gasdynamics in each of the wave rotor passages as they rotate past the various ducts. The model can operate both on and off-design, allowing dynamic behavior to be studied throughout the operating range of the wave rotor. The model accounts for several major loss mechanisms including finite passage opening time, fluid friction, heat transfer to and from the passage walls, and leakage to and from the passage ends. In addition, it can calculate the amount of work transferred to and from the fluid when the flow in the ducts is not aligned with the passages such as occurs in off-design operation. Since it is one-dimensional, the model runs reasonably fast on a typical workstation. This paper will describe the model and present the results of some transient calculations for a conceptual four port wave rotor designed as a topping cycle for a small gas turbine engine.
Paxson, D. E.↗
Preliminary results on the gravitational field of the moon from analysis of lunar orbiter tracking data
Gravitational field of moon from numerical analysis of Lunar Orbiter tracking data
Gapcynski, J. P.↗
VSAERO analysis of structurally decoupled tip planforms for a semispan wing
A numerical analysis has been conducted with the three-dimensional panel code VSAERO for two interacting lifting surfaces that are separated in the spanwise direction by a narrow gap, with the angle of attack of the outboard section being set independently of the inboard section, as in the 'free tip' rotor blade system proposed for helicopters. Computed values of tip surface lift and pitching moment coefficients are correlated with experimental data to determine the most suitable method for modeling the gap region between the surfaces. It is shown that the induced drag of the tip surface is reduced for negative incidence angles relative to the inboard section.
Martin, Daniel M.↗
Experimental and Numerical Study of Coating Thickness Using Multi-slot Air Knives
Gas-jet wiping is a widely employed production technology for controlling the final zinc coating thickness on a moving substrate during continuous hot-dip galvanizing. This paper presents an experimental investigation and numerical analysis of a prototype multi-slot air knife, which offers an increase in wiping efficiency relative to the traditional single-slot jet geometry in the continuous galvanizing process. The applicability of the analytical coating weight model of Elsaadawy et al. (Metall Mater Trans B, 38:413-424, 2007) to predict the final coating weight was determined for the multi-slot geometry, where particular focus was devoted to the effect of geometric parameters. Experimental measurements under a variety of knife geometry and process conditions agreed with the coating weight predictions of the analytical model. It was also shown that the air-knife geometric parameters had a significant effect on the pressure profile and shear stress distribution applied by the air knives to the moving substrate. It was determined that the final coating thickness was significantly affected by the auxiliary jet width, D{sub a}, where lighter coating weights at higher strip velocities (up to 5.4 pct at V{sub s} = 1.5 m/s) could be achieved by using the multi-slot air-knives prototype vs. the conventional single-slot configuration.
36 MATERIALS SCIENCE↗
Simulating combustion of a seven-component surrogate for a gasoline/ethanol blend including soot formation and comparison with experiments
Combustion of a seven-component surrogate for a research grade 87 octane gasoline mixed with 10% ethanol is investigated experimentally and numerically from the perspective of an isolated droplet burning under conditions that promote one-dimensional gas transport. The numerical analysis included a kinetic mechanism comprised of 398 species and 24,814 reactions and a soot model that accounted for nucleation, surface growth, coalescence/aggregation of soot particles, and luminous flame radiation. Measurements of droplet and flame diameters were made for an initial droplet diameter (D o ) of approximately 0.63 mm. The simulations agreed well with the measurements including the location of the soot shell. Preferential vaporization was revealed by simulations of the liquid concentrations in the droplet. Predicted peak soot volume fractions coincided with temperatures between 1300 K and 1400 K as a soot inception temperature. Simulations were also carried out for D o between 0.25 mm and 5 mm to explore the effect of radiation and D o on burning. Below 0.25 mm radiation was negligible and burning rates and flame temperatures converged to a single value. Increasing D o up to 1.8 mm lowered the burning rate with luminous radiation having a strong effect. When radiation was entirely removed from the model the burning rate was nearly constant. Above D o = 2 mm droplets extinguished almost immediately after ignition. The flame temperature decreased with increasing D o while it increased when radiation was omitted. As a result, the simulations show that soot precursors including polyaromatic hydrocarbons were concentrated around the soot shell.
42 ENGINEERING↗
Trends in computerized structural analysis and synthesis; Proceedings of the Symposium, Washington, D.C., October 30-November 1, 1978
The subjects considered are related to future directions of structural applications and potential of new computing systems, advances and trends in data management and engineering software development, advances in applied mathematics and symbolic computing, computer-aided instruction and interactive computer graphics, nonlinear analysis, dynamic analysis and transient response, structural synthesis, structural analysis and design systems, advanced structural applications, supercomputers, numerical analysis, and trends in software systems. Attention is given to the reliability and optimality of the finite element method, computerized symbolic manipulation in structural mechanics, a standard computer graphics subroutine package, and a drag method as a finite element mesh generation scheme.
Noor, A. K.↗